It is frequently necessary to use hypodermic syringes for intravenous administration of fluids, or to withdraw fluids from the veins of a person during the course of treatment of an illness, or in routine diagnostic examinations. Hypodermic syringes used for this purpose are generally disposable, and are intended to be discarded after a single use by trained medical personnel.
However, unless they are properly disposed of, these used syringes present a serious health hazard to persons subsequently handling them. For instance, if the needle is left intact and is not sheathed in a protective guard, it is possible that someone could be accidentally pricked with the needle during subsequent handling of it. If the syringe has been used to make an injection or withdraw body fluid from a person having an infectious disease, the consequences could be very serious to someone accidentally pricked with the needle.
One of the more serious concerns of health care workers is the danger of becoming accidentally infected with HIV-infected blood or other materials. Acquired Immune Deficiency Syndrome (AIDS) is now recognized as an epidemic of global proportion. In addition, there is an increasing recognition of a broad spectrum of severe HIV-associated diseases, including pneumonia, endocarditis, and pulmonary tuberculosis.
Medical and rescue personnel are aware of these risks, and when possible, take precautions to avoid unnecessary exposure or contact with infectious materials.
However, if a used syringe has been left intact and not properly disposed of, medical and rescue personnel, custodial workers, and others, are exposed to the danger of being accidentally pricked with the contaminated needle in spite of the precautions that they might normally take. Such a needle could be mingled with soiled linens, bandages or other materials, and when these materials are gathered for disposal, the needle has the distinct potential of penetrating the skin of anyone handling the materials.
To prevent such accidents from occurring, the needles should be broken from the used syringes, and/or encased in a protective sheath, and devices have been provided in the prior art for accomplishing this.
For instance, needles have been joined to the syringe body through frangible connections so that the doctor, nurse or other medical personnel can easily break the needle from the syringe after it is used. Unfortunately, this is not always done during the urgency of medical treatment, or if it is, there still remains an exposed needle body.
Similar shortcomings exist with respect to guards or sheaths that have been provided to encase the used needle. Such guards generally comprise separate sleeves or cap members that enclose the needle before it is used and which must be removed and set aside during use of the syringe. It is intended that after use of the needle, the guard will again be placed over the needle. However, the guard may become misplaced during the medical procedure being performed and therefore not available for reuse. Even if it is not misplaced, the person responsible for safe handling of the syringe may not have the time, or take the time, to retrieve the guard and place it over the needle.
A further problem exists with respect to syringes that are not properly disposed of or rendered inoperative after use. Used syringes of conventional construction are capable of reuse, and are thus liable to spread infectious diseases.
Although the medical community has long used disposable syringes a single time and then disposed of the used syringe, these syringes are sometimes stolen from hospitals, or from medical equipment suppliers, or are not properly disposed of after being used by authorized personnel, and ultimately come into the possession of drug abusers. Intravenous drug abusers consistently use the same syringe over-and-over again and share them with other drug abusers. This practice has led to the rapid spread of HIV, Hepatitis and other infectious diseases in the illicit drug use population.
Intravenous drug use is believed to account for most AIDS-related diseases in heterosexual men and women. This disease may also be transmitted to the children of infected adults, and to the sex partners of the infected persons, or to others, such as medical workers and rescue personnel, who may be inadvertently exposed to the blood of the infected person.
As AIDS-related diseases continue to grow, it is becoming increasingly more important to control the means by which these diseases are transmitted. Medical personnel, for example, should have reasonable assurance that they can perform their procedures without unnecessary risk of exposure to such infectious diseases, and without requiring time-consuming steps to render used syringes safe for subsequent handling.
Some examples of prior art syringes that utilize needle guards are shown in U.S. Pat. Nos. 2,550,394, 2,551,339, 2,566,428, 2,607,341, 4,365,626, 4,778,453, 4,782,841, 5,064,419 and 5,088,985. However, none of these patents teach the use of the plunger as a needle guard after the syringe has been used. U.S. Pat. No. 5,064,419 has a retractable needle that is displaced into the syringe barrel and piston following use of the syringe. U.S. Pat. No. 5,088,985 discloses an arrangement in which a needle remover (28) is normally fitted within the plunger body, but which may be removed and placed over the needle to separate it from the syringe. U.S. Pat. Nos. 2,550,394, 2,551,339, 2,566,428 and 2,607,341 all disclose arrangements in which a needle guard used during shipment and handling of the syringe is removed and inserted into the barrel to serve as a plunger when the needle is ready to use. In order to reuse the plunger as a guard following its use in any of these patents would require separation of the plunger from the piston, and would require an inventive step not suggested in any of the prior art.
In addition to an effective needle guard, a means is needed to prevent sharing and reuse of syringes by intravenous drug abusers, and thereby to prevent the spread of infectious diseases caused by use of contaminated syringes. Since the major cause of spread of HIV, Hepatitis and similar diseases is through the repeated and/or shared use of contaminated hypodermic syringes and needles, a significant preventive measure would be the elimination of the ability of intravenous drug abusers to acquire syringes that could be used more than one time.
Examples of some prior art efforts to provide non-reusable syringes are disclosed in U.S. Pat. Nos. 3,478,937, 3,951,146, 4,367,738, 4,391,272, 4,493,703, 4,731,068 and 4,781,684. Most of these patented devices involve some type of catch mechanism which becomes engaged upon full or partial travel of the syringe piston to lock the piston in place and prevent either its withdrawal or its insertion into the syringe barrel. Other devices disclosed in these patents include pistons which become separated from the plunger or stem after an operating cycle to eject a fluid from the syringe. For instance, U.S. Pat. Nos. 4,391,272, 4,731,068 and 4,781,684 disclose arrangements in which both some type of catch mechanism and a separable piston and stem structure are used.
All of the prior art devices known to applicant are either excessively complicated and expensive in construction or are not adequately reliable in operation. Further, many prior art devices require either modification of the barrel, or the use of separate collars, adapters or sleeves to connect the piston to the plunger or stem. Moreover, it is possible in some of these devices to reassemble them after use, whereby they may then be repeatedly used.
Accordingly, it would be desirable to have a disposable hypodermic syringe that is reliable in operation, simple and economical in construction, and in which a part of the syringe assembly, itself, is adapted as a needle guard after the syringe has been used for its intended purpose. It would further be desirable to provide a disposable syringe that is not capable of being reused after a single use.